In transmission of an image by a facsimile machine, transmission information such as the date and time and number of pages is added onto the transmitted image as a header or footer in order that the receiving side may readily confirm the sender of the image and the number of pages in the transmission.
In a facsimile machine of the type which stores transmitted data in memory in the form of raw data and transmits the data after it is compressed, a very large memory is required when raw image data is stored. In conventional facsimile machines of this type, therefore, the raw data is stored in memory after it has been compressed. In a case where the aforementioned transmission information is added onto this data, however, use is made of a procedure in which the data that has been stored in memory is expanded and restored to raw data at the time of transmission, data relating to the transmission information is added onto this raw data, the resulting data is then compressed again and transmitted after compression.
Since this procedure involves data compression and expansion at the time of transmission, processing takes time. This problem becomes particularly acute when dealing with a large amount of data.
For example, ITU-T Recommendation T.81 recommends using the JPEG standard as the scheme for encoding a color image. If transmission information is added onto a color image, therefore, the conventional technique requires a procedure involving expanding data that has undergone JPEG compression, adding on a transmission header and then performing compression again. However, color image data involves much more data as compared with monochrome image data and compression/expansion of this data takes too much time. This conventional technique is not very practical for this reason.